1. Field of the Invention
The present invention relates to a laminated glass assembly prepared by bonding glass plates having a thickness of 1.5 to 2.5 mm together.
2. Description of the Prior Art
Laminated glass assemblies have been prepared by bonding two sheets of glass plates together with an intermediate plastic layer such as polyvinyl butyral layer. These laminates have been widely used as front windshields for automobiles. The two glass plates used in the standard laminated glass assemblies for use as windshields in automobiles have a thickness of about 2.5 to 5 mm. The development of thinner laminated glass assemblies in wich thinne glass plates are used, is required from the standpoint of decreasing the weight of the automobile and from the standpoint of safety for occupants in an automobile collision. However, laminated glass assemblies prepared from bonded glass plates having a thickness of less than 2.5 mm have often been broken from shock delivered to the edges of the laminated glass assemblies, in the transportation of laminated glass assemblies and when the assembly is embedded in the frame of an automobile. Accordingly, the handling of such thin laminated glass assemblies has been difficult and cumbersome for practical uses. In order to overcome these difficulties, laminated glass assemblies prepared by bonding thin tempered glass plates have been proposed. However, glass plates having a thickness of less than 2.5 mm could not be satisfactorily tempered by the conventional air quenchtempering method because the plates possess unsatisfactory quenching coefficient. Accordingly, when a glass plate having a thickness of less than 2.5 mm is tempered, it has been necessary to use special tempering methods such as chemically tempering by ion-exchange, or thermally tempering by liquid quenching. In these techniques, a large apparatus and long operating periods have been required and the handling of the plates during the tempering operations is inconvenient. Moreover, the yield is not high enough and it is very difficult to quickly prepare laminated glass assemblies at low cost in mass production.